The comments on the post seem to indicate that those closing thought it was unclear. It has nothing to do with your answer -- well, not exactly anyway.
When you edit a post or answer a question, it bumps the question back to the front page of the website. When you answered the question, that put it back on the front page and that meant people would notice it. Maybe they hadn't before, maybe they did, who knows.
But this time, it got put on the front page and enough people voted to put it on hold that it is now there, pending clarification. It's also started to accumulate reopen votes, so at least somebody disagrees with the close reason.
Most likely the question slipped through unnoticed early on and when it got bumped to the front page, it opened it up for inspection again and at least 5 people found it to be unclear.